Electrically insulating composition



July 30, 1940. P. NowAK Er AL A 2,209,928

ELEQTRICALLY INSULATING COMPOSITION Filed NOV. 16. 1957 IYIVeTTboYs: Paul Nowak, Hevm ahh Hofmeiex;

by y a HehA Attorney,

Patented July 3 0, V194() ELECTRICALLY INSULATING COMPSITION Paul Nowak and Hermann Hofmeier, Berlin- Charlottenburg, Germany, assignors to General Electric Company, a corporation of New York Application November 16, 1937, Serial No. 174,888

In Germany December l0, 1936 5 claims` (ci. 2st-42) The present invention relates to electrical cables. It is more particularly concerned with cables comprising a conductor insulated with a composition comprising vulcanized polymerized4 acrylic acid `or its homologues, or vulcanized polymerized derivatives of acrylic acid or homologues thereof. Compositions of this kind are described in the co-pending application oi Paul Nowak, Serial No. 749,476, filed October 22, 1934, now Patent No.`2,105,361, and in our co-pending application, Serial No. 33,898, filed July 30, 1935, now Patent No. 2,105,362, both of which patents are assigned to the same assignee as the present invention. In the following description of the invention and in the appended claims, the class of polymers above mentioned is designated, generally, as polymerized acrylic acid derivative.

In accordance with the present invention compositions comprising vulcanized polymerized acrylic acid derivatives are modified to improve their physical characteristics. More particularly, it may be stated that compositions produced as described in the aforementioned applications are given increased compressive strength both at normal and at elevated temperatures,.

without sacriiicing any of their other desirable characteristics, by incorporating therewith polymerized chloroprene (polymerized chloro-2-butadiene-1,3).

In the accompanying drawing, Figs. l. and 2 represent cross-sectional views or" single-conductor cables enclosed in a sheath of our irnproved insulating composition; and Fig. 3 shows a similar view of a multi-conductor cable comprising three single-conductor cables insulated as shown in Fig. 2.

The reference numeral I designates the metallic conductor; 2, conventional electrically insulating material such, for example, as paper, rubber, asbestos, spun glass, varnished cambric, etc.; 3, the insulating composition of the present invention; 4, conventional filling material, such as jute, asbestos or the like, for bringing a multiconductor cable to uniform cross-section; and 5, an armored covering. Like numerals designate like parts in all figures.

In Fig. 1 the new insulating material is shown as being superposed directly on a metallic conducting core. In Fig. 2 conventional insulating material is shown as being superposed directly on the conductor and the composition of this invention constitutes the external sheath. Fig. 3 shows three individualvconductors insulated as shown in Fig. 2, and the whole surrounded by an armored covering, with lling material in the intervening space between the individiu'il conductors and the armored covering.

The following specific examples illustrate how the new electrically insulating compositions of this invention may be prepared:

Example 1 Parts by weight Polymerized ethyl ester' of acrylic acid Preferably the polymerized ethyl acrylate is plasticized prior to mixing with the other ingredients, for example, by incorporating therewith a suitable amount of dibutyl phthalate.

The specied components may be lineaded together at about 89 to 90 C. in a suitable mixing apparatus, for example, a Banbury mixer, iollowed by working on heated mixing rolls. il. small amount, :for instance, about l5 parts by weight, of an anti-oxidant such as beta nephthol may be incorporated in the above-described mass during the kneading operation.

lli desired, the polyacrylate, adsorbent and nller, with or without the sulfur, may be separately mixed, after which the polymerized vchloroprene or the chloroprene and the sulfur (ii the sulfur was not previously added) may be incorporated with the said mixed or reacted components. Under certain conditions it may he preferred to mixV first the polyacrylate and' earth, activated bleaching clay, activated bauxite,

and the like. Talcum, French chalk orother powdered lling materials may be used. By selecting polymerized chloroprene of different hardnesses, it is possible to produce compositions of a harder lor softer nature, as desired or as conditions may require.

Example 2 i Parts by weight Polymerized ethyl ester of acrylic acid 318 Powdered adsorbent (surface-active) material 195 Powdered, inert (non-active)v inorganic iilling material 467 Sulfur A 2 Polymerized chloroprene 32 to 320.

The powdered adsorbent in the foregoing formula preferably is active carbon (for example, active gas soot). A small amount, for instance, about 18 parts by weight, of an anti-oxidant such as beth-naphthol may be incorporated with the above-mentioned components. The description given under Example 1 with respect to plasticizing the polyacrylate, to methods and temperatures of combining or mixing thecomponents, and to the adsorbent material,'filling material and polymerized chloroprene employed, 'is also an. cable to this example.

Compositions produced in a manner such asdescribed under the foregoing illustrative examples are soft and yielding, and after the mixing operation readily may be extruded upon a metallic conducting core (for example, solid-or stranded copper wire)` at an elevated temperature, for instance, at about 100 to 120 C. 'I'he insulated conductor ordinarily is given a vulcanizlng heat treatment in order to effect or to complete vulcanization of the applied insulating 'i composition `and particularly Vulcanization of the derivative in the presence of surface-active materials (adsorbents), as is done in making the compositions of this invention, is fully described inthe aforementioned Nowak application, Serial.

No. 749,476, now Patent No. 2,105,361.

'Ihe compositions used in making the insulated conductors or cables of the present invention preferably comprise vulcanized polymerized acrylic acid ethyl ester and polymerized chloroprene in an amount by weight corresponding to from yabout 10 to 100 per cent that of the said ester.

Specic examples of acrylic compounds that may be employed in practicing this invention are, for instance, polymerized acrylic acid, polymerized methyl, ethyl, propyl, butyl `and higher alkyl esters of acrylic and methacrylic acids,

polymerized acrylonitrile, or mixtures of two cr more such substances.

Our improved insulating composition is characterized by its high compressive strength both at normal and elevated temperatures, and by its excellent resistance to oil, water, ozone, aging and iniiammability, Which-characteristics are reected in the improved electrical cables of this invention. v

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. An insulating material adapted for insulating an electric cable, said material consisting of an oil, waterand ozone-resistant composition comprising the reaction product of a mixture containing polymerized chloroprene, polymerized acrylic acid derivative and a vulcanizing agent said polymerized chloroprene increasing substantially the compressive 'strength of the said composition. 2. An insulating material adapted for insulating a metallic conductor, said material consisting of an oil, Waterand ozone-resistant composition containing polymerized chloroprene and polymerized ester of acrylic acid co-reacted with sulfur in the presence of an adsorbent, said polymerized .chloroprene increasing substantially the compressive strength ofthe saidcomposition both at normal and at elevated temperatures.

3. An electrically insulating composition comprising polymerized ethyl ester of acrylic acid, polymerized chloroprene in an amount by Weight corresponding to from about 10 to 100 per cent that of the said ester, sulfur and an adsorbent,

the said polymerized materials being conjointly reacted with the sulfur in the presence of the adsorbent, and the said composition being oil, waterand ozone-resistant and having a higher compressive strength both at normal and elevated temperatures than a composition containing no polymerized chloroprene but with all other `components and proportions thereof substantially the same.

4. An electrically insulating composition comprising a ller and the reaction product of a vulcanizing agent with a mixture containing polymerized chloroprene and polymerized acrylic acid derivative, said polymerized chloroprene increasing substantially the compressive strength of the said composition both at normal and at elevated temperatures.

5. An oil, waterand ozone-resistant electrically insulating composition comprising the product of vulcanization of a mixture containing approximately Parts by Weight Polymerized ethyl ester of acrylic acid 500 Powdered adsorbent material 200 Powdered inert inorganic filling material 280 Sulfur Polymerized chloroprene; 50 to 500 said composition'having a higher compressive strength both at normal and at elevated temperatures than a composition containing no polymerized` chloroprene but with alll other components ,and proportions thereof vsubstantially the same. 'f

PAULNOWAK.` g, HERMANN HOFMEIER, 

